1. The Field of the Invention
The invention relates to devices, methods, and systems for managing data libraries. Specifically, the invention relates to devices, methods, and systems for switching library managers in a data library system.
2. The Relevant Art
Systems of mainframe computers or servers frequently maintain large data libraries. Data libraries typically contain many storage devices including hard disk drives, tape drives, and optical storage drives. Computers retrieve data from and store data to the storage devices in the data library through a device controller.
A computer, usually a host computer, issues a data transaction command to the device controller. The device controller employs one or more library managers to coordinate accessing data in the data library. The library manager schedules and executes the data transaction command on the storage devices.
A system administrator often must switch library managers from a first library manager to a second library manager. Switching library managers typically requires that the storage devices in the data library be forced offline and that the data transaction commands awaiting execution be canceled. The first library manager is suspended and the second library manager is activated. Storage devices must be varied online or restarted before the second library manager can resume receiving and executing data transaction requests. Library managers may also be switched by taking the data library offline and allowing the data transaction commands awaiting execution to complete. The data library must be varied online to resume standard data library operation.
FIG. 1 is a block diagram illustrating a representative data library system 100 of the current technology. The system 100 includes one or more host computers 105, one or more library managers 110, one or more storage devices 115, and a device controller 120. The system 100 shows the functional elements of a data library.
The host computer 105a issues a data transaction command to the device controller 120. The device controller 120 assigns the data transaction command to the first library manager 110a for data to be retrieved from or saved to the storage device 115. The first library manager 110a directs a storage device 115 to complete the command. The depicted data library system 100 also includes a second library manager 110b. 
A system administrator switches library management functions from the first library manager 110a to a second library manager 110b. In the depicted system, the system administrator forces the storage devices 115 offline and suspends the first library manager 110a from accepting data transaction commands. Previously accepted data transaction commands are lost. The system administrator then activates the second library manager 110b and varies the storage devices 115 online, allowing the second library manager 110b to execute data transaction commands.
In other systems, the system administrator takes the data library system 100 offline and allows previously accepted data transaction commands to complete. The system administrator suspends the first library manager 110a and activates the second library manager 110b. The data library system 100 is varied online or otherwise placed on-line to resume data library operations.
FIG. 2 is a flow chart diagram illustrating a library manager transition method 200 of the current technology. The method 200 includes a force storage device offline step 205, a notify host step 210, a take library offline step 215, a switch library manager step 220, a vary storage device step 225, an inform host step 230, and an end step 235.
A system administrator activates the method 200. The force storage device offline step 205 forces the storage devices 115 in the data library system 100 offline. The notify host step 210 communicates to the host computer 105 that the data library retained by the storage devices 115 will be unavailable. The take library offline step 215 takes the data library offline, making the library inaccessible to the host computer 105.
The switch library manager step 220 commands the first library manager 110a to suspend library management functions. The step 220 further directs the second library manager 110b to activate library management functions. The vary storage device step 225 varies the storage devices 115 online under the management of the second library manager 110b. The inform host step 230 communicates to the host computer 105 that the data library has resumed accepting data transaction commands. The end step 235 terminates the method 200.
Taking storage devices 115 or the data library system 100 offline lengthens the time required to switch library managers and slows data processing functions. Data library functions would be enhanced if library managers could be switched without taking storage devices 115 or the data library system 100 offline.
What is needed is a method for switching library managers while the data library remains online. What is more particularly needed is a device, method, and system for switching library managers while maintaining storage devices online.